FIG. 12 illustrates a perspective view of a coil bobbin 101 disclosed in Japanese Unexamined Patent Publication No. 11 (1999)-122855 as the first prior art. The coil bobbin 101 comprises a core tube 114 around which wires are wound to form a coil and flanges 115 provided on both axial ends of the core tube 114. The coil is formed by concentrated winding around the coil bobbin 101 and then attached to a stator (not shown).
As the second known art, a cassette coil 201 is shown in FIGS. 13 and 14. FIG. 13 illustrates a front view of the cassette coil 201. FIG. 14 illustrates a view of the cassette coil 201 seen from the back of a flange 215, the view from which a flange 216 to be described later is excluded for convenience of explanation. As shown in FIGS. 13 and 14, the cassette coil 201 is provided with an insulator bobbin 210 for forming the coil. The insulator bobbin 210 has a core tube 214, around which wires 213 are wound to form a coil, and a pair of plate-shaped flanges 215 and 216 provided at both axial ends of the core tube 214. Further, the flange 215 at one end of the core tube 214 is formed with a cutout portion 212. FIGS. 13 and 14 illustrates the coil, which is formed from the insulator bobbin 210, around which, the wire 213 is wound.